Space Debris: A Tragedy of the Orbital Commons

Why dead satellites and fragments crowd Earth's orbits, how this resembles the tragedy of the commons, and the policies proposed to keep space usable.

Earth’s orbits are becoming crowded. Along with thousands of working satellites, there are dead satellites, spent rocket stages and many fragments from collisions and explosions. This space debris travels at very high speeds, fast enough that even small pieces can badly damage a satellite.

How much debris?

The European Space Agency estimates there are tens of thousands of tracked debris objects larger than about 10 centimetres, and around a million pieces between 1 and 10 centimetres, plus far more smaller fragments.

A tragedy of the commons

Orbits are a commons: no country or company owns them, and everyone can use them. Each operator benefits from launching satellites, but the risk of collisions and debris is shared by all. Without rules, operators have weak incentives to limit debris or remove dead satellites, a classic tragedy of the commons.

The Kessler syndrome

In 1978, NASA scientist Donald Kessler warned that if debris became dense enough, collisions could create more fragments, causing further collisions in a chain reaction. This Kessler syndrome could make some orbits unusable for generations.

Events that added debris

In 2007, China destroyed one of its own weather satellites with a missile, creating thousands of fragments.
In 2009, a working U.S. communications satellite collided with a defunct Russian satellite.
In 2021, Russia destroyed one of its satellites in a missile test, creating a large debris cloud.

Possible solutions

Deorbiting rules: requiring satellites to leave orbit within a set time after their missions end. In 2022, the U.S. Federal Communications Commission adopted a rule requiring many satellites in low orbit to deorbit within five years of mission end.
Debris removal missions, being developed by start-ups and agencies.
Fees or taxes on orbital use: some economists have proposed charging satellite operators for the collision risk they create.
International agreements, such as bans on destructive anti-satellite tests, which several countries have pledged.

The orbital parking fee

Researchers including Akhil Rao have proposed an "orbital-use fee", charging operators for each satellite in orbit based on the risk it creates for others. Like a congestion charge on roads, it would make operators account for the costs they impose on everyone else, encouraging fewer idle satellites and more responsible behaviour.

Thinking space is too big to fill up

Space is vast, but useful orbits are limited, and debris spreads along popular orbital paths. Collisions can make particular orbits dangerous long before space is "full".

Key takeaways

Space debris includes dead satellites, rocket stages and fragments travelling at high speed.
Orbits are a commons, creating a tragedy of the commons without rules.
The Kessler syndrome warns of chain-reaction collisions.
Deorbiting rules, debris removal, orbital-use fees and test bans are proposed solutions.